Early life stage exposures to environmental contaminants can result in aberrant pancreatic ?-cell development, which may predispose an individual to diabetes. A common mode of toxicity shared by numerous, diverse environmental contaminants is the generation of reactive oxygen species (ROS) and oxidative stress. ROS and cellular redox potential play fundamental roles in normal embryonic development and cell signaling. Perturbation of these processes resulting from contaminant exposure can alter cell fate decisions, resulting in functional or structural alterations that only become apparent with subsequent stress or age. However, surprisingly little is known about how embryos respond to oxidative stress, or the impact of toxicant exposures on pancreas development. The long-term goal of this research is to understand how embryos respond to oxidative stress, and how toxicant exposures contribute to the developmental origins of diabetes. The zebrafish (Danio rerio) is a well-established, widely used, and powerful model organism for studying vertebrate embryonic development in vivo. To investigate how changes in the developmental redox microenvironment affect toxicant sensitivity and pancreatic ?-cells at specific stages, we will us a fluorescent redox biosensor, redox imaging, and automated, time-lapse microscopy of transparent, transgenic zebrafish embryos exposed to environmental contaminants. This project will focus on environmentally relevant concentrations of persistent toxicants previously implicated in the etiology of diabetes (PCBs, phthalates, and the Teflon surfactant PFOS). We will examine the relationship between the most abundant antioxidant defense, glutathione (GSH), and the transcription factor Nrf2, that regulates the response to oxidative stress. Our specific aims are: 1) elucidate the relationship between GSH and contaminant activation of Nrf2 during embryonic development and create an embryo redox map; 2) determine how an oxidant exposure history affects Nrf2 activation and toxicant sensitivity, 3) ascertain the roles of oxidative stress, GSH, and Nrf2 activation in deviant pancreatic ?-cell development, and identify critical sensitive windows of pancreas organogenesis. This research will lead to a mechanistic understanding of how early life chemical exposures and oxidative stress may damage the developing pancreas and predispose humans to diabetes and potentially other diseases. This work will also elucidate a poorly understood, but critical fundamental biological process- the role of the redox environment in embryonic development- and identify specific targets for mitigation and translational toxicology.